A great number of neurotransmitter receptors and scaffolding molecules such as PSD-95 are present in the postsynaptic density (PSD) of neural synapses. These molecules play important roles in the formation and structural maintenance of the PSD. Furthermore, cytomatrix proteins such as Bassoon and RIM are present in the cytomatrix that constitutes the presynaptic active zone (i.e., the cytomatrix at the active zone; CAZ). These proteins play crucial roles in the formation and structural maintenance of the active zone. The efficient transmission of signals between synapses is extremely important in learning, and in the construction and maintenance of memories. Hence, it is easy to envision that failure of this process will cause various neuropathic and neurodegenerative disorders.
Numerous molecular groups associated with the molecular mechanism for axonal guidance of neurons (pathfinding) have been identified by analyses using flies and nematodes, enhancing the understanding of the mechanism to a certain extent. However, in subsequent synaptogenesis, much remains to be clarified as to what kind of molecules are temporally and spatially involved in the formation of mature synaptic contacts.